Two Mammalian Models Can Use Their Intestines to Breathe; Finding May Be Applicable to Humans with Respiratory Failure, Including Those with COVID-19

Rodents and pigs share with certain aquatic organisms the ability to use their intestines for respiration, finds a study published online on May 14, 2021 in the journal Med. The article is titled “Mammalian Enteral Ventilation Ameliorates Respiratory Failure.” The researchers demonstrated that the delivery of oxygen gas or oxygenated liquid through the rectum provided vital rescue to two mammalian models of respiratory failure. "Artificial respiratory support plays a vital role in the clinical management of respiratory failure due to severe illnesses such as pneumonia or acute respiratory distress syndrome (ARDS)," says senior study author Takanori Takebe (@TakebeLab), MD, PhD, of the Tokyo Medical and Dental University and the Cincinnati Children's Hospital Medical Center. "Although the side effects and safety need to be thoroughly evaluated in humans, our approach may offer a new paradigm to support critically ill patients with respiratory failure." Several aquatic organisms have evolved unique intestinal breathing mechanisms to survive under low-oxygen conditions using organs other than lungs or gills. For example, sea cucumbers, freshwater fish called loaches, and certain freshwater catfish use their intestines for respiration. But it has been heavily debated whether mammals have similar capabilities. In the new study, Dr. Takebe and his collaborators provide evidence for intestinal breathing in rats, mice, and pigs. First, they designed an intestinal gas ventilation system to administer pure oxygen through the rectum of mice. They showed that without the system, no mice survived 11 minutes of extremely low-oxygen conditions. With intestinal gas ventilation, more oxygen reached the heart, and 75% of mice survived 50 minutes of normally lethal low-oxygen conditions. Because the intestinal gas ventilation system requires abrasion of the intestinal muscosa, it is unlikely to be clinically feasible, especially in severely ill patients--so the researchers also developed a liquid-based alternative using oxygenated perfluorochemicals. These chemicals have already been shown clinically to be biocompatible and safe in humans.